The present invention relates to a stabilizer for vinyl chloride resin, and particularly it relates to a novel stabilizer for vinyl chloride resin which is not only superior in compatibility with vinyl chloride resin but also is capable of demonstrating a satisfactory lubricity effect and is high in safety from the viewpoint of toxicity.
Polyvinyl chloride is generally inferior in thermal stability and undergoes thermal degradation during processing thereof, so that various metallic soaps are usually added thereto as stabilizer. Among the applicable metallic soaps for this purpose, cadmium stearate demonstrates various excellent effects including, it has a satisfactory compatibility with compounds and a lubricity effect, and a resin mixed therewith is superior in workability, it imparts printability of the product, and in the case of manufacturing transparent articles, it imparts to the product a high degree of transparency, so that cadmium stearate has been commonly employed as a stabilizer for flexible and rigid vinyl chloride resins.
However, in the case of food-packaging materials or tablewares made from vinyl chloride resin containing cadmium stearate, there is a danger that the toxicant cadmium will effuse and will be taken into the human body during the use of these articles, and at the factory manufacturing cadmium stearate, there arise troubles with respect to the safety of the working personnel or environmental pollution. Therefore, there have been attempts to use calcium salt or barium salt of lauric acid or myristic acid as a substitute for cadmium stearate. However, these substitutes are all defective in that the length of the chain of the fatty acid therein is so short that the lubricity effect thereof is unsatisfactory. In this connection, when the foregoing substitutes are employed as the stabilizer, compounds are apt to adhere to the calendering roll or the embossing roll, and in an extreme case, it becomes impossible to perform calendering or embossing. Besides, the transparency of the product is deteriorated as compared with that in the case of employing cadmium stearate.
Under such circumstances, with a view to making up for the defects of the foregoing substitutes, it has also been attempted to improve the lubricity effect by jointly applying stearic acid, calcium stearate or the like. In this case, however, there arise such troubles as the printability of the product deteriorates and besides the applied stabilizer effuses onto the surface of the product. Accordingly, in this field of industry, there is a need for a novel stabilizer for vinyl chloride resin which will have an efficiency comparable with that of cadmium stearate while providing safety with respect to the toxicity.